Image-recording elements of the type to which this invention relates typically comprise a support material having thereon an ink-receiving layer. The elements include those intended for reflection viewing, which usually have an opaque support, and those intended for viewing by transmitted light, which usually have a transparent support.
A very wide variety of different types of ink-receiving layers have been proposed heretofore. For example, U.S. Pat. No. 3,889,270 describes ink-receiving layers consisting of a protein, a polysaccharide, cellulose, a cellulose derivative, polyvinyl alcohol, a copolymer of vinyl alcohol, gelatin, albumen, casein or silica gel; U.S. Pat. No. 4,371,582 describes ink-receiving layers containing a basic polymer latex; U.S. Pat. No. 4,528,242 describes ink-receiving layers comprising a mixture of a carboxylated polymer and a polyalkylene glycol; and British Patent Applications No. 2 134 129 A and No. 2 147 003 A describe ink-receiving layers comprising a polymeric binder, a water-soluble salt of a polyvalent metal and a cationic organic material such as salts of alkylamines, quaternary ammonium salts, polyamines and basic latexes. Many patents describe ink-receiving layers comprising a pigment dispersed in a polymeric binder. Examples of such patents include U.S. Pat. Nos. 4,269,991, 4,425,405, 4,446,174, 4,474,847, 4,474,850 and 4,478,910.
Many different types of inks adapted for use in devices such as pen plotters and ink jet printers are also known and have been described in numerous patents such as, for example, U.S. Pat. Nos. 4,155,768, 4,176,361, 4,197,135, 4,395,287, 4,396,429, and 4,409,039.
While the image-recording elements and inks proposed heretofore are extremely diverse in nature, there are many unresolved problems in the art, and many deficiencies in the known products which have severely limited their commercial usefulness. The requirements for use of these inks and recording elements are very demanding. For example, the combination of ink and recording element should exhibit:
(1) rapid-drying characteristics such as result when the ink-receiving layer has the ability to rapidly absorb the ink,
(2) controlled spreading characteristics such that the image is clearly and sharply defined,
and
(3) high image density such as results when the dye or pigment present in the ink is deposited at or near the surface of the ink-receiving layer.
In addition to being of high density, it is also desirable that the ink image be abrasion-resistant so that it is not easily rubbed off, smear resistant, so that it can be subjected to normal handling without risk of smearing, and waterfast, so that it is not harmed by contact with water or other aqueous liquids such as might come into contact with the element as a result of spills or other accidental exposure to liquids. The hydrophilic ink-receiving layer must also be waterfast to avoid removal of the ink image through dissolution or damage to the layer itself, and should also be non-blocking to facilitate packaging and handling.
As pointed out in U.S. Pat. No. 4,308,542 (see lines 40-68 of Column 1), U.S. Pat. No. 4,371,582 (see line 38, Column 2 to line 27, Column 3), and U.S. Pat. No. 4,554,181 (see lines 35-61 of Column 1), these objectives impose seemingly contradictory requirements which make the resolution of the problem exceedingly difficult. The solution proposed by U.S. Pat. No. 4,308,542 is to use a synthetic pulp paper as the recording medium and heat-treat the paper to fuse the synthetic pulp, but this has the serious disadvantage of requiring a costly and time-consuming additional step in the image-forming process. The solution proposed by U.S. Pat. No. 4,371,582 is the use of a basic latex polymer as the ink-receiving layer while U.S. Pat. No. 4,554,181 proposes use of a combination of a water-soluble polyvalent metal salt and a cationic polymer; but these techniques are often of only limited effectiveness and do not provide as high a degree of abrasion resistance and waterfastness as is desired.
It is toward the objective of providing a simple, inexpensive and readily implementable solution to the problem of meeting the diverse needs of image-recording elements adapted for use in such devices as pen plotters and ink jet printers that the present invention is directed.